Medications are often administered to a patient intravenously by what is known as a piggy-back set-up. Generally, in such a system a catheter is located in a patient's vein and connected by a delivery tube to a "Y" connector. One branch of the connector is coupled through a one-way valve to a primary reservoir which contains a primary medication that is to be administered for a prolonged time period, e.g., saline, dextrose, or the like liquids. The other branch of the connector is coupled to a secondary reservoir into which a secondary medication has been placed with or without dilution.
For proper system valve operation, the secondary reservoir must be hung higher than the primary reservoir. This generates a greater head of pressure from the secondary reservoir to maintain the valve in a closed position, preventing the flow of primary medication. When the secondary reservoir is exhausted, its head of pressure drops and the valve opens, allowing the flow of primary medication to the patient. See for example U.S. Pat. Nos. 4,237,880 to Genese 4,256,103 to Mylrea and 4,258,712 to Harms et al.
Piggy-back systems unfortunately require two reservoirs, one for the primary medication and one for the secondary medication. Such systems also require two separate sets of tubing, a connector, a valve device, and related flow control apparatus. Such an extensive amount of equipment not only complicates the use of the system, but also greatly adds to its cost. Additional tubes are necessary where it is desired to provide different administration rates for the primary and secondary medications. Control of administration can also be complicated by the varying relative heads of pressure in the two reservoirs and the need to properly locate the reservoirs with respect to each other. Other devices require that air be admitted to displace medication, thus creating the risk of contamination.
Accordingly, it is desirable to provide a medical device which avoids the shortcomings of prior systems and automatically sequentially administers plural medications to a patient. The device of the present invention meets these desires and avoids the necessity of two reservoirs that must be positioned at certain respective elevations. The present device also has a relatively uncomplicated structure and is relatively easy to use.